Preparation of esters of formic acid

ABSTRACT

N,N-DIALKYL (2-HALO-1-SUBSTITUTED ETHOXYMETHYLENE) IMMONIUM HALIDES ARE FORMED BY HALOGENATION OF OLEFINES IN THE PRESENCE OF N,N-DILOWER ALKYL FORMAMIDE TO FORM NEW COMPOUNDS AND DERIVATIVES. THE COMPOUNDS ARE DECOMPOSED TO VALUABLE 1,2-DIHALOCOMPOUNDS, 1-HALO-2FORMATES AND HALOHYDRINS BY THERMAL DECOMPOSITION, HYDROLYSIS OR ALCOHOLYSIS.

United States Patent 3,786,084 PREPARATION OF ESTERS OF FORMIC ACID Pierre Marie Joseph Ghislain de Radzitzky dOstrowick, 101 Avenue Paul Hymans, and Alain Joseph Guillaume De Roocker, 149 Avenue des 'Capricorne, both of Brussels, Belgium No Drawing. Filed Jan. 12, 1973, Ser. No. 322,988 Int. Cl. C07c 17/00, 29/00, 67/00 US. Cl. 260-491 1 Claim ABSTRACT OF THE DISCLOSURE N,N-dialkyl (2-halo-1-substituted ethoxymethylene) immonium halides are formed by halogenation of olefines in the presence of N,N-dilower alkyl formamide to form new compounds and derivatives. The compounds are decomposed to valuable 1,2-dihaloc0mpounds, 1-halo-2- formates and halohydrins by thermal decomposition, hydrolysis or alcoholysis.

This is a division of application Ser. No. 22,031, filed Mar. 23, 1970.

The present invention is directed to N,N-dialkyl (2- halo-1substituted ethoxymethylene) immonium halides and to an improved method of preparing these compounds by direct reaction.

The N,N-dialkyl (Z-halo-l-substituted ethoxymethylene) immonium halides have the structure H [an]... R

wherein n is an integer of 1 to 3; R are identical lower alkyl radicals having from 1 to 3 carbon atoms; Hal are identical halogen atoms of the group consisting of chlorine and bromine; R are hydrocarbon radicals having 1 to 9 carbon atoms, R being a monoradical selected from the group consisting of alkyl radicals having 1 to 8 carbon atoms and cyclic hydrocarbon radicals having 5 to 6 carbon atoms in the ring such as cyclopentyl, cyclohexyl and phenyl radicals, said cyclic hydrocarbon radicals having 0 to 3 ring substituents of the group consisting of halogen atom and lower alkyl radicals having 1 to 3 carbon atoms when n is 1; R being a diradical selected from the group consisting of alkyl radicals having 1 to 6 carbon atoms and of 1,3- and 1,4 benzenic diradicals when n is 2; R being a 1,3,5-benzenic triradical when n is 3.

The starting olefine compound for the manufacture of the compounds having the above formula may be any terminal olefin such as l-heptene, 4-methyl-1-pentene, 1- hexene, 1,6-heptadiene, vinylcyclohexane, vinylcyclopentane, styrene, mand p-divinylbenzene, 1,3,S-trivinylbenzene, m-ethyl-styrene, p-ethylstyrene, m-methylstyrene, m-chlorostyrene, and p-propylstyrene. Thus, in general, the olefines are aliphatic monoor diolefines including the CH=CH group, monoand polyvinyl benzenes and their lower alkyl and halo ring derivatives.

N,N-dialkyl (2-halo-1-substituted ethoxymethylene) immonium halides of this invention are formed by reacting the olefine with halogen in the presence of an equimolar, preferably an excess, of dilower alkyl formamide at ambient to lower temperatures. N,N-dimethyl formamide is especially suitable, although other lower dialkyl formamide such as diethyl or dipropyl formamide may be used, the dimethyl being the most economically available industrially.

The dialkyl formamides possess a basic character which helps to prevent the hydrogen chloride or bromide, evolved from side reactions, from adding onto the olefinic double bond instead of chlorine or bromine. It is bene- 3,786,084 Patented Jan. 15, 1974 ficial to use the dialkyl formamide in excess of the stoichiometric amount. For one equivalent of olefinic function, one mol of chlorine or bromine and at least one mol of dialkyl formamide are used, an excess of between 0.01 and 4 mols of the latter being beneficial. Said excess can be higher, such as up to ten mols without impairing the reaction.

As the immonium halide is either a crystalline solid or a viscous oil, an excess of dialkyl formamide enables the medium to be kept fluid until the addition of halogen is completed.

The reaction can be practiced. by mixing the olefinic compound with the dialkyl formamide, and then introducing the halogen. Another advantageous manner of operation consists in adding simultaneously and in stoichiometric amount the halogen and the olefin to the dialkyl formamide, the latter being possibly in excess. In some cases it may be advantageous economically to dissolve the halogen into the dialkyl formamide and add the resulting solution to the olefin either pure or dissolved beforehand into the dialkyl formamide. Thus there are many methods of carrying out the reaction, but it is advisable to avoid contacting the olefine with a great excess of halogen in order to minimize side reactions.

The preparation of the immonium halides according to the process of the present invention is preferably carried out at a temperature in the range of 20 C. and +40 (3., preferably between -20 C. and +10 C. At higher temperatures the immonium halide thermally decomposes into the addition product of the halogen onto the olefinic double bond.

For isolating the immonium halide, it is advantageous to keep the reaction mixture at a comparatively low temperature in order to prevent any decomposition. The salt commonly consists of a crystalline precipitate, which can be separated from the excess of dialkyl formamide by filtration.

Sometimes it is convention to add an inert solvent, wherein the immonium halide is not soluble, in order to promote filtration and wash the crystals. Ether, carbon tetrachloride, benzene and heptane are all useful and suitable solvents. The crystals may be dried under vacuum and must be kept away from moisture in order to prevent any decomposition by hydrolysis. In the case where the immonium halide consists of a viscous oil, it can be separated by settling, and purified by washing with ether or with another of the amove-mentioned solvents.

The N,N-dialkyl (Z-halo-l-substituted ethoxymethylene) immonium halides are useful intermediates in the preparation of dihalogen adduct derivatives of the starting olefines by thermal decomposition, 1-halo-2-formates by hydrolysis, and halohydrins by alcoholysis. Each of these decomposition products are useful fire retardants for incorporation into readily combustible polymers and plastics. For instance, polystyrene containing these fire retardants which is ordinarily readily combustible, cannot be ignited or, if ignited at high temperature, is self extinguishing. The formation of these intermediates is illustrated by the following reactions:

(a) Thermal decomposition It therefore appears that thermal decomposition of immonium halides results in the addition product of the halogen onto the olefin, while regenerating the dialkyl formamide with an almost [quantitative] yield. This combination of reactions comprising the synthesis of immonium halide and its thermal decomposition is especially interesting, as the direct addition of chlorine into an olefin is always accompanied with side reactions such as de hydrochlorination or substitution. For instance, direct chlorination of styrene yields, even at a very low conversion, maximum three parts of the desired 1,2-dichloro-1- phenylethane for one part of 2-chloro-1-phenylethylene. When an attempt is made to increase the conversion, important amounts of 1,2,2-trichloro-l-phenylethane are formed. 1,2-dichloro-l-phenylethane may easily be transformed into phenylacetylene which is an important monomer in the synthesis of heat stable polymers.

By hydrolysis for formyloxy group and one atom of chlorine or bromine are linked onto the double bond, while the dialkyl amine hydrochloride or hydrobromide is formed.

Alcoholysis makes it possible to obtain the halohydrin of the olefin and an alkyl halide, while the dialkyl formamide is regenerated.

Other characteristics and inherent advantages will become apparent from the examples herein which illustrate the practice of the present invention.

EXAMPLE I This example illustrates the preparation of N,N-dimethyl (Z-chloro-l-phenylethoxymethylene) immonium chloride.

(CH3 2['C6H5CH N+.Cl resulting from the addition of N,N-dimethyl formamide and chlorine onto styrene.

At C. and within forty-five minutes, in the dark and under anhydrous conditions, 71 grams (1 mol) of chlorine and a mixture of 104 grams (1 mol) of styrene and 150 grams of N,N-dimethyl formamide are introduced simultaneously into a flask equipped with an agitating device and containing 142 grams of N,N-dimethyl formamide (4 mols totally). A white precipitate of the immonium chloride is gradually formed. At the end of the reaction, 200 milliliters of ether are added, then the precipitate is separated by filtration, Washed with ether, dried under vacuum at room temperature, all this under anhydrous conditions.

Thus 192 grams i.e. 77% immonium chloride of the above formula is obtained. When ether is replaced with benzene, heptane or carbon tetrachloride, practically identical results are obtained. When the total amotunt of dimethyl formamide is reduced to 2 mols, the yield of immonium chloride is 75.5%. The excess of dimethyl formamide, together with a little of 1,2-dichloro-1-phenylethane, can be recovered by distillation of the filtrate.

When the aforesaid immonium chloride undergoes gradual heating, it decomposes between C. and G, into N,N-dimethyl formamide and 1,2-dichloro-1- phenylethane which may be separated and recovered almost quantitatively by distillation, preferably under reduced pressure of about 10 mm. Hg.

EXAMPLE II The reaction of Example I is carried out except that the chlorine is replaced with 1 mol (160 grams) of bromine.

A 39.5% yield of the corresponding immonium bromide of the formula (CH3 2 CsH5-CH N .Br

boiling point: -110" C., under 4 mm. Hg refractive index: n 1.5538

Dimethylamine hydrobromide is recovered, with a quantitative yield, by concentration of the aqueous phase.

The 2-bromo-l-phenylethylformate may be added to polystyrene to impart fire retardant characteristics to this polymer.

EXAMPLE III The reaction is carried out exactly according to the process of Example I, except that m-chlorostyrene is substituted for styrene.

N,N-dimethyl[2-chloro 1 (m-chlorophenyDethoxymethylene1immonium chloride.

is obtained with a yield of 68%.

Analysis of this product gave: Calculated (percent): carbon, 46.70; hydrogen, 4.98; chlorine, 37.60; nitrogen, 4.95. Found (percent): carbon, 46.15; hydrogen, 5.42; chlorine, 34.88; nitrogen, 5.04.

EXAMPLE IV Proceeding as in Example I, but substituting for the styrene m-ethylstyrene, N,N-dirnethyl[2-chloro-1-(m-ethylphenyl)ethoxymethylene]immonium chloride is obtained having the formula Analysis of this product gave: Calculated (percent): carbon, 56.50; hydrogen, 6.93; chlorine, 25.65; nitrogen, 5.07. Found (percent): carbon, 56.78; hydrogen, 6.57; chlorine, 25.42; nitrogen, 4.81.

EXAMPLE V Proceeding as in Example El, 'but substituting for the styrene l-heptene, N,N-dimethyl(2-chloro-l-pentyl-eth oxymethylene)immonium chloride is obtained having the formula in a 32% yield.

Analysis of this product gave: Calculated (percent): carbon, 49.60; hydrogen, 8.75; chlorine, 29.30; nitrogen,

5.80. Found (percent): carbon, 50.23; hydrogen, 8.25; chlorine, 28.50; nitrogen, 5.67.

EXEAMPLE VI In the dark and under anhydrous conditions, 71 grams (1 mol) of chlorine is introduced at 0 C. and within ninety minutes into a flask equipped with an agitating device and containing a mixture of 66.5 grams (0.5 mol) of m-divinylbenzene and 74 grams (1.01 mol) of dimethyl formamide. Benzene 1,3 bis[dimethyl(2-chloro-1-ethoxymethylene)immonium chloride], a viscous oil, is precipitated from the reaction mixture by means of ether.

By vacuum distillation under mm. Hg, between 40 C. and 45 C., N,N-dimethyl formamide, contaminated by a small amount of its chlorhydrate, is recovered.

When the pressure is decreased gradually to 2 mm. Hg, 3.3 grams of a fraction boiling up to 150 C. is obtained, then 112.5 grams of m-bis (1,2-dichloroethyl) benzene (an 83% yield), is obtained boiling between 150 C. and 160 C.

When eight mols of dimethyl formamide are used for one mol of divinylbenzene, m-bis (1,2-dichloroethyl) benzene is obtained with an 88% yield.

EXAMPLE VII The reaction is carried out as in Example I, except that an equimolar amount of N,N-diethyl formamide is substituted for the N,N-dimethyl formamide.

N,N-diethyl (2-chloro-l-phenylethoxymethylene) immonium chloride is thus obtained having the formula What is claimed is:

1. The method of forming a compound having the formula H O R C-O-J):

H- --Ha1 H wherein n is an integer of 1 to 3; Hal are identical halogen atoms of the group consisting of chlorine and bromine; R being a mono-radical selected from the group consisting of alkyl radicals having from 1 to 8 carbon atoms and cyclic hydrocarbon radicals of the group consisting of cycloalkyl radicals having 5 to 6 carbon atoms in the ring and phenyl, said cyclic hydrocarbon radicals having 0 to 3 ring substituents of the group consisting of chlorine, bromine atoms and lower alkyl radicals having 1 to 3 carbon atoms, when n is 1;, R being a diradical selected from the group consisting of alkyl radicals having 1 to 6 carbon atoms, 1,3- and 1,4-benzenic diradicals, when n is 2; R being a 1,3,5-benzenic triradical when n is 3, comprising reacting a halogen selected from the group consisting of chlorine and bromine with at least an equivalent quantity of an N,N-dilower alkyl formamide and an olefine hydrocarbon of the formula R{-CH=CH where R and n are as defined above at a temperature of approximately 20 C. to +40 C. to form a N,N-dialkyl (Z-haIo-I-substituted ethoxymethylene) immonium halide of the formula -Halwherein R, n and Hal are as defined above and R is a lower alkyl radical and then hydrolyzing said compound into 1-halo-2-formates of said first formula.

References Cited UNITED STATES PATENTS OTHER REFERENCES Chem. Abstracts, 17:3158 Chem. Abstracts, 341626 Chem. Abstracts, 72:89716 v.

VIVIAN GARNER, Primary Examiner US. Cl. X.R.

2528.l; 260--453 R, 488 CD, 617 R, 618 D, 633, 648 C, 648 R, 651 R, 652 R 

